Photographic silver transfer product and process, including a lead salt



Jan. 29, 1952 E. H. LAND 2,584,029

PHOTOGRAPHIC SILVER TRANSFER PRODUCT AND PROCESS, INCLUDING A LEAD SALTFiled April 13, 1946 FlG.l

PHOTOSENSITIVE LAYER I O BASE LAY E n IMAGE CARRYING LAY ER I V INVENTORBY fl ng AT ORNEY Patenied Jan. 29, 1952 PHOTOGRAPHIC SILVER TRANSFERPROD- UCT AND PROCESS, INCLUDING A LEAD SALT Edwin H. Land, Cambridge,Mass., assignor to Polaroid Corporation, Cambridge, Mass., a corporationof Delaware Application April 13, 1946, Serial No. 662,000

29 Claims.

This invention relates to photography and more particularly to novelphotographic film units and materials, and methods for utilizing suchfilm units and materials.

More specifically, a preferred form of the present invention relates toimprovements over the novel photographic film units and processesdisclosed in my copendin-g application Serial No. 576,254 filed February5, 1945, for Photographic Process, Apparatus and Product, now abandoned.It is, however, not limited to use with such processes or films.

The principal object of the present invention is to provide photographicmaterials and processes which enable the production of a positive imagehaving increased contrast, gamma and stability.

Another object of the invention is to provide a photographic imagehaving a pH varying in accordance with the density of said image, saidpH being high in the shadows and low in the highlights.

Another object of the invention is to provide a composite photographicfilm unit comprising a photosensitive layer, an image-carrying layer anda container having therein a liquid composition, said liquid compositioncomprising a solvent for a developer and an alkali, said film unithaving therein a developer and an alkali, said imagecarrying layerhaving associated therewith a substance capable of reducing thealkalinity of said image-carrying layer when said liquid composition isspread in contact therewith.

Another object of the invention is to provide in a photographic processof the type wherein a layer of photosensitive material is treated with aliquid composition, including a developer, and a positive image iscreated by transferring image forming components from said layer toanother layer, the improvement which comprises increasing the contrastand gamma of said image by forming said image in thepresence of a substance capable of reducing the alkalinity of said image in thehighlights thereof.

A still further object of the invention is to provide a photographicprocess which comprises treating a layer of exposed photosensitivematerial with an alkaline liquid composition contain ing a developer, analkali, and a substance capa ble of forming image-forming componentswith nents to another layer and creating on said other layer a positiveimage having dense blacks and clear highlights by reacting saidimage-forming components. with said alkaline liquid composition andpreventing the oxidation of any excess developer in the area of saidhighlights by reducing the alkalinity of said liquid composition in thearea of said highlights to a point where oxidation of said developerdoes not occur.

A still further object of the invention is to provide a photographicsheet material capable of acting as a carrier for a final positive imagewhen formed into a permeable assembly with an undeveloped exposedphotosensitive layer and permeated with a liquid composition containinga solvent, a developer, a material for forming positive image-formingcomponents and a film-forming material, said sheet material havingassociated therewith a substance capable of reacting with saidfilm-forming material to form therewith compounds less soluble in waterthan said film-forming material.

These and other objects of the invention will in part be obvious andwill in part appear hereinafter.

In one form of the present invention there is provided a compositephotographic film unit having a photosensitive layer and another layer.The other layer may serve several functions. In

a preferred example it acts as a backing layer topermit the spreadingof. a liquid composition in a layer parallel to the photosensitive layerand it also performsthe additional function of serving as a carrier forthe final positive image. In less preferred forms of the invention itserves only either one of these functions or merely acts to carrycertain of the reactive ingredients. In a1- most all cases, however, itwill have the additional function of forming, with the photosensitivelayer, a unit only slowly permeable to oxygen and within which aphotographic reaction may take place with substantial freedom from theeffects of aerial oxidation. This layer is referred to as animage-carrying layer. Between these two layers there is included arupturable container or pod having therein a liquid composition. Thiscomposition is preferably viscous, preferably alkaline and preferablycontains therein a developer and a film-forming material. The liquidcomposition also preferably contains a substance which will react withthe unexposed portions of the photosensitive layer to form therewithsoluble image-forming complexes. When the pod is ruptured and theviscous developing composition tion of the film-forming substance which,dur- I 3 ing the processing of the film, is converted from a fluid to asolid. The positive image-forming complexes are transferred from thephotosensitive layer to, the image-receiving layer, where the positiveimage is formed. The photosensitive layer is next preferably strippedfrom the imagereceiving layer to reveal the finished positive image.

The present invention deals primarily with the improvement of the aboveprocess and product by increasing the stability, contrast and gamma ofthe resultant image and the insolubility and dimensional stability ofthe formed film. The present invention is not limited to use with-theabove product or process, however.

For a fuller understanding of the nature and objects of the inventionreference should be had 7 to the following detailed description taken inconnection with the accompanying drawings, wherein: 1

Figure 1 isan exaggeratedcross-sectional view of ;a preferred embodimentof -.the present inven-.

tion; and r I Fig. 2 is an exaggerated cross-sectional view of anotherembodiment of thepresent invention.

As shown in Fig. *1, there is providedxa base layer In adapted to carryon one surface thereof a photosensitive layer H. There is also providedan image-carrying layer [2 which may be joined to the base layer til-bymeans of a hinge I l. Between-the image-carrying layer 1 2 and thephotosensitive layer l i, there is positioned aconloseacetate, celluloseacetate propionate, brother substances capable ofsupportingalphotosensie tive-emulsion. 7

This base .canbe madeopaque, if desired, by

the addition of suitable dyes or pigments to the above-named substances,or the base. :lllfcan be made or paper and-other.materialssuitable .forsupporting a photosensitive emulsionopacity will be preferable dependingupon .how the film is exposed within the camera. :It may also be made ofan impermeablesubstance.such

asglass.

The photosensitive layer is preferably of the type rendered developable.by exposure .to light, e. g., an emulsion of a silver halide, or ofamixture of silver halides or of a mixed-:silver halide.

The image-carrying layer H2, in a'preferred embodiment. of theinvention, :is Iformed of a photographic material, known in .theartasbaryta paper, although it can be made .of other substances. Thislayer is preferably pern eableto a substance contained in the liquidcomposition and may also be manufactured from other sub stances such asgelatin or paper. It may also be made of gelatin, regenerated cellulose,.polye hydroxy alkanes such as polyvinyl .alcohol,'.s,odium alginate,certainof the cellulose etherssuch as methyl cellulose, and theirderivatives such as sodiumcarboxymethyl cellulose or hydroxyethylcellulose, carbohydrates such as gums or starch, and mixtures of thesematerials where Such 4 v the latter are compatible. It may, however, bemade of relatively impermeable materials such as glass, Celluloid andother materials commonly used in the photographic arts.

The liquid composition, in its preferred embodiment, is composed of adeveloper such as hydroquinone, a film-forming substancefsuch as sodiumcarboxymethyl cellulose, and a substance adapted to form from a latentphotographic image a posi- V tive image-forming component. This lattersubstance in a preferred form of the invention is sodium thiosulfate.There are also preferably in cluded other substances to aid thephotographic -reaction,-such as a preservative, i. e. sodium sulfite,and an alkali, i. e. sodium hydroxide, plus water to carry theabovementioned elements in solution, Suitable liquid compositionsmay beproduced as shown in the following nonlimiting examples.

Example #1 The following substances are put in a beaker.

and stirred with ,aplastic rod until dissolved:

Water -cc 47.6 7 Sodium sulfite (desiccated) ;grams, .18 Sodiumhydroxide do 117.5

The following substance isthen stirred into'the above mixture witha'plasti'c rod to avoid lumps:

Sodium carboxymethyl cellulosemedium viscos' ity (Lot No. i155Hercules), 42.62'grams. The above mixture is stirred in a closedjmixerhaving a nitrogen atmosphere over "the liquid therein, and thetemperature is raised .t'ol'TB" The mixture is maintained at thistemperature Ex mple #2 The following substances are put in a'beaker andstirred with a plastic rod until dissolved:

. Water cc 476 Sodium sulfite' (desiccated) grams 9 Sodium hydroxide doV 19.50

The following substance'is then stirred into the above mixture withaplastic rod to avoid lumps: Sodium carboxymethyl cellulose, mediumviscosity (Lot No. 1155 Hercules),'4;2.62 grams.

The above mixture isstirred in a closed mixer 7 having a nitrogenatmosphere over the. liquid therein, and the temperature is raised to178 F. The mixture is maintained at this temperature for approximately3% hours. During the first two hours 2.5 grams of sodium-tliiosulfateare added to the above, mixture. During the last hour of heat treatmentsgrams of hydroquinone are'adde'dto the mixture; 237 cc. of water are Ithen added to the mixture sometime before the completion'of the '3/zhour heating period.

Various equivalents maybe used in the above-- mentionedliquidcomposition and it isequally possible to substitute for the thickeningand'film forming sodium carboxymethyl cellulose other film-forming:agents; such as hydroxyethyl cel-.

lulose, or gelatin, or such materials as sodium alginate, or starch.Equally, other developers,

preservatives and alkaliesmay be used, and other substances such asrestrainers may beadded.

In the use of the invention as described above,

the photosensitive layer isexposed; to ia'ctinic' light a Ell and,without further exposure to light, the whole assembly is subjected to amechanical stress such as by passing through a wringer, not shown,starting with the hinge end 14. As the film is squeezed through thewringer, the container [3 is ruptured and the liquid composition isuniformly spread between the photosensitive layer H and theimage-carrying layer i2.

When the liquid composition is spread between the photosensitive layer Hand the image-carrying layer l2, the following reaction takes place: thedeveloper develops the latent photographic image and the sodiumthiosulfate dissolves the unexposed silver halide grains and carriesthem into the image-receiving layer, being formed by the solidificationof the film-forming substance contained in the liquid composition. Theseunexposed silver halide grains are then developed and formed into apositive image. While this process is in operation stated above, thefilmforming substance, i. e. the sodium carboxymethyl cellulose, isbeing solidified into a dimensionally stable film,

It has been found that it is possible to substantially improve theproducts and processes described above by increasing the insolubility ofthe image-receiving layer, increasing the contrast of the positiveimage, increasing the gamma, increasing the density of the transferredimageforming components, and insolubilizing various unexhausted elementsof the liquid composition.

The above can be accomplished by placing preferably within or upon theupper surfac of the image-carrying layer I2 a material which enters intothe photographic reaction to bring about the results set forth above. Ofthe materials which have been found satisfactory, those showing the mostextraordinary results are generally the lead salts, and, of the leadsalts, lead acetate appears to be the most desirable. In the preferredmodification of the invention, imagecarrying layer I2 is coated with asolution of a lead salt such as lead acetate,,ancl the solvent isallowed to evaporate, leaving within and upon the surface of the layer12 a precipitate of lead acetate. When the above-described photographicprocess is practiced and the liquid composition is spread between thephotosensitive layer II and the lead acetate coated layer l2, the leadacetate is taken into solution by a solvent (water) in the liquidcomposition, and substantially improves and increases the contrast,gammaand stability of the final positive image. It whitens thehighlights and increases the density of the shadows.

All of the reactions involved in this substantial improvement of thequality and stability of the final positive image are not completelyunderstood, and in some cases, it is difficult-to differentiate betweencause and effect in the various reactions which are going onsimultaneously. There are, however, certain reactions which can be setforth with a considerable degree of certainty. In the first place, it isquite definitely known that the lead acetate reacts with a polymericsubstance such as sodium carboxymethyl cellulose to form cross-linkagestherewith and thereby create a compound having an increased insolubilityin water. This is believed to hasten the precipitation of thefilm-forming sodium carboxymethyl cellulose, thereby speeding up theformation of the image-receiving layer. The compound resulting from theinteraction of the lead acetate and the sodium carboxymethyl cellulosegives a more dimensionally stable film, having an increased insolubilityin water.

The lead acetate remarkably increases the con trast and gamma of thepositive image produced in the image-receiving layer, although it is notcompletely understood how this effect is accomplished. There are certainobserved conditions which would explain this improvement of the positiveimage, but the reason for the existence of these conditions is notreadily ascertainable from a theoretical analysis of the variousreactions. The positive image formed in the presence of lead acetate hasvery much denser blacks than a positive image formed under exactly thesame circumstances wherein lead acetate is not used. Thisintensification of blacks is believed to be caused by an increase in theamount and size of the silver grains forming the positive image. Aremarkable increase in intensification is provided by the use of leadsalts generally and lead acetate in particular. It is believed that thelead reaction with the sodium carboxymethyl cellulose changes thecharacter of the film being formed to such an extent that the'silverformed therein is formed in larger grain sizes, whereby a greaterdensity is achieved, and less scattering of light results.

It has also been observed that an image produced without the use of amaterial such as lead acetate has a more or less overall uniformalkalinity; while an image produced with the use of :lead acetate has aremarkable variation in pH from point to point, and it has been foundthat those images having th clearest whites and the darkest blacksshowed a condition which was slightly acid or neutral, i. e. a pH of6-8, in the highlights and quite basic, i. e. a pH of above 9, in theshadows. It is believed that this slightly acid or neutral conditionplays an extremely important part in at least the preservation of clearwhites. One of the reasons for believing this is that those images,lacking clear highlights, are apparently stained by an oxidation productof the developer. Such a stain is eliminated when lead acetate is usedin sufiicient quantity to convert the highlights to a slightly acid orneutral con dition. It is believed that this is due to the fact that thedeveloper is incapable of being oxidized in a neutral or slightly acidsolution. Therefore, no stain can form even though a potentialstainforming component exists in the Whites which is made inactive bythe lower pH. The presence of this stain-forming component in thehighlights has been experimentally ascertained by taking a positiveimage, having clear highlights, produced with a lead acetate-coatedimage-carrying layer and placing a drop of sodium hydroxide on a clearhighlight. This sodium hydroxide raises the pH considerably and a brownstain appears.

In the preferred form of the invention, lead acetate is used as theinsolubilizing agent. This lead salt seems to be particularly efficientfor accomplishing the results mentioned above and is quite easily usablesince it is soluble in water.

A preferred method of incorporating the lead acetate in theimage-carrying layer I2 is as follows:

1575 grams of lead acetate are dissolved in 3500 cc. of water. shallowcontainer and heated to approximately -90 F. A continuous roll ofdouble-weight baryta paper is then passed over the lea-d acetate bathfor approximately two minutes. The paper is suspended near the bath byrollers in such a way that only one surface thereof will contact thebath. Thus, only one surface is coated. After passing through the bath,the paper. is passed This mixture is placed in a ovena dryingdrum"which'isheatedto approximately 75i-I-909 F. The coated surface of: thepaper is in contact with the :drum :for approxia mately 'l minutes- Thisis a preferred method or coating lead acetate 1 upon. double-weight y apaper, but otherimethods may equally be used.

This method of coating the barytapaper is; preferredsince it places thepoisonous leadracee 'tateonttheinner surface only of. theimagecarryinglayer. Thus, in-the handling of thefilm pack the fingers'xofa-a user 'donot :contact the Of course, when; the film iunit h'as b'een processed inthe :manner.

lead acetate-coatedsurface.

describedabova thelead has combined with the materials usediand hasformed insoluble salts.

Despite .the'eformation of. these insoluble salts. it isstronglyrecommended that care beusedin-x handlingcthefinished picture,lest some'soluble- The finished picture should lead-salts remain. not:be placed inthe mouth.

In-uvi'ew: of-the factthat lead salts are highly poisonous,.;anotherpreferred former: the present invention embodiesz-xtheuseof .a leadsaltwhich isinsoluble in water. As an example of this,

thereiisiusemlead tartrate which is deposited uponandiwithin the surfaceof 'the irnage-carrye ing;:laye1"l2. With: lead .tartrate used in placeof a wateresolubleilead'salt, such as lead acetate, the leadtartratewill. not'normally be removed frQmithealayerJZ' by -handling. Forinstanceit willi'znot beipicked..up..by the fingers of a user' though.thisrlead salt-is insolublein water. It is believed that this eifect isdue to the sodium.

hydroxide which apparently dissolves the lead tartrate and: formstherewith insoluble compoundsmore slowly than the other elements of the.combination: thus the lead is in ionic conditionfor reaction with theother elements of the composition.

Numerousother lea'dsalts, such as lead nitrate, lead bromide leadchlorate, lead perchlorate, lead .citrate,;lead. isobutyrate, leadperoxydisulfate,'or lead dithionatemay be used inthe practice-of.-thepresent invention. The lead salts may. be used singly or jointly; forexample, excellent results have' been'obtained with an image-carryiinglayer firsttcoatedwith lead acetate'and'then with leadenitrate.

Since lead-salts are. extremely poisonous, personsworking withthesesalts. should u'tilize the nOrmalprecauticns -.-practiced with any useof I lead salts. 7

Someoithese .leadsalts. areinsoluble in Water but solublein othersubstances. If those solvents are-not normally included in the liquidcomposition, they-areadded so that the'liquid composi tion will dissolvethe lead salt. If it is undesirable to include-this solvent-incombination with the other-elements of the liquid composition for toolong a time, a separate container is included ton-carry the solvent;

Zinc acetate 'frnay.. also be usedfor whitening:

' forming material.

the. higl-1lights.-:. This;;materlal:-..may. be .1- placedzlwithin'andzupon; the surface-rofsthe;imageecarry ingrrlayerx, l 2 in.the same .manner ;as practiced The zinc acetate is also takenintossolution by a solvent 2 therefor con. tainedwin: theliquidvcomposition' and reacts in much thesame-way-except that itdoesnot in solubilize the sodium carboxymethyl. cellulose.v

with the lead salts.

It does,;however., whiten-the highlights.

It isq.-believed that. .the beneficialresults. ob-. tained'vwith thezinc acetate are. due v partly to. its ability to-reduce I thealkalinity=inv the neighL- borhoodof. the highlights of the positive image...

Ithas-salsa been .found that. it .is -possible.to practice the presentinvention by. incorporating; an agent such as alead salt inor upon thelowers surface-of the photosensitive layer... In this in:

s'tance the operation is. the same end, and asthe liquid composition isspread between the photo-.. fsensitiveelayer'. and .the imagesupportlayer,.it.}.

issolves the leadsaltfrom the photosensitive. layer andlthe leadsaltacts inthesame manner.

as described above.

When-the lead .saltiis. carriedby the-photosensitivelayer,precautionsshould .be taken. to; insure that the .leadsalt is in. astratum. separate.

from. the photosensitive..material since the lead salts appeantohave a-.strongdesensitizingeffect on the photosensitive material;

It isialsdpracticable tocarry the agent, such.

as aleadsalt, out of contact with eitherthe photosensitivelayer orthesupport layer.

Since the leadjsalt hasa coagulating effect. upon. some .,of thefilm-forming. materials used in'the present invention, it. is preferredin this embodiment of theinvention. to have the lead salt anda.solvent1thereforcontained in a separate container or.pod.. A meansfor. accom-,.

plishingthis resultLis-shown in Fig.2 where like numbers correspondtolike numbers in .F'ig.v 1 As shown here, a. separate container. I?) maybe placed immediately; adjacent the container l3 carrying .the liquid.composition. Thus, when the..film..is. exposed and .processed.byrunning througlra wringer, thelead salt solution is re-. leasediand isspread,along with the liquidlcoma position, between-the photosensitivelayer and.

the image-carrying; layer. 7

those. cases where; a. film-forming sub-, stance is used which isnothardened by a lead salt, the .lead salt-has. theability to increasethe: contrast-and, gamma: of the final positive, even.

though it'may notinsolubilize any vformed film.

Examples: of such film-forming materials are:

hydroxyethyl cellulose 'and' polyvinyl alcohol.

In someuinstances it is desirable to'practice the'presentinvention:without :the use of .a film-' If 1 such:v be. the case, the=-photographic processfis substantially the same as that. described =above=andi the final positiveimage risformedpn and within the surface ofInfsuch 'amodificatlOIlxOf the-invention, the lead salts havea'very theimage-carrying :layer.

beneficial. effect upon. the final. image,-. increasingits:stabilitmncontrast. and gamma; Zinc.

acetate. similarly; increases ;the--clearness of the highlights whenused jwithwa liquid-composition having vno film-formingmaterial.

Another;v though" less preferred, method of practicing; the presentinvention -.is to. have oer-r tainof thegmaterials'which are preferablyincluded .in' the-liquid composition-placed elsewherein sthefilm units.For instance, it is;pos: sible to deposit thedeveloper andhypoin solid;form on the iInage-carryingz layer; In this." a

case, the. container might have therein only water or' an aqueoussolution of sodium carboxymethyl cellulose.

A This sheet can be placed between the photosensitive layer II and theimage-carrying layer 12. Thelayer l2 has thereon an insolubilizing agentsuch as lead acetate. In this modification of the invention, thecontainer has only therein a solvent, such as water, for the variousmaterials incorporated into the extruded sheet. When the water is spreadin contact with this extruded sheet, it dissolves the sheet and theremainder of the process is the same as that discussed in connectionwith Fig. 1.

One advantage of this last-mentioned modification is that it eliminatesthe necessity for a liquid container and in this case the film unit maybe processed by merely wetting it in a water bath until a sufficientamount of water has been absorbed by the film unit to give the desiredconcentrated solution of the reactive materials.

It is equally possible to place such an extruded sheet between the baselayer in and the photosensitive layer ll, although in this latter caseit is desirable to include an additional film-' forming material withinthe water carried by the container, since it is desirable to form thefinal positive image in a film created during the process.

It should also be understood that, although the invention has beendescribed in terms of individual film units, it may be practiced withroll films wherein a. plurality of images are produced and the roll filmmay be treated so as to produce each image separately or all imagessimultaneously.

The use of soluble lead salts, and specifically lead acetate, in silverhalide transfer processes is also disclosed in certain other of mycopending applications, such, for example, as Serial No. 700,931, filedOctober 3, 1946, for Photographic Product and Process, and Serial No.708,007, filed November 6, 1946, for Photographic Product and Process.

Since certain changes in carrying out the above process, and certainmodifications in the article which embody the invention may be madewithout departing from its scope, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A photographic product comprising a photographic product comprising aphotosensitive material which includes a silver halide layer, a baselayer for receiving, by transfer, a positive print, and a rupturablecontaining means holding a liquid, said product having positionedtherein photographic reagents including a silver halide developer, asilver halide solvent and a lead salt soluble in said liquid, saidcontaining means and said layers being i so held together that saidcontaining means is capable, upon rupture, of releasing at least part ofits contents to permeate superposed portions of said photosensitivelayer and said base layer, said liquid, upon release, rendering saidsilver halide developer and said silver halide solvent sensitive layerand to form soluble silver complexes with the undeveloped silver halideof said photosensitive layer and, additionally, providing a solution ofthe lead salt adjacent the surface of the print-receiving area of saidbase layer in which part at least of the soluble silver complex isreduced to silver to produce the positive print.

2. The product of claim 1 wherein the liquid is a dispersion of afilm-forming organic colloid, and the lead salt is capable of reactingwith said colloid to give a reaction product less sol-.

uble in said liquid than said colloid.

3. The product of claim 1 wherein the lead salt is lead acetate.

4. The productof claim 1 whereinxthe lead salt is lead tartrate.

5. The product of claim 1 wherein the containing means comprises asingle elongated enclosure which contains all of said liquid, and anelongated dispensing lip which parallels said enclosure and isrupturable to provide a passage for said liquid.

6. The product of .claim 1 wherein the containing means comprises a pairof liquid-containing enclosures, each including a rupturableliquid-dispensing lip'zfor providing a passage therefrom to saidimage-receiving area, the liquid in one of said enclosures comprising adispersion of the silver halide solvent and the silver halide developer,and the liquid in the other of said enclosures comprising a dispersionof the lead salt.

7. The product of claim 6 wherein the disper sions are solutions.

8. A photographic product comprising a photosensitive silver halidelayer, a base layer, and a rupturable container holding a liquid, saidlayers and said container being attached together so as to permit saidlayers to be superposed with said container so positioned as to releaseits liquid for spreading in a film between said layers, the liquid insaid container comprising a silver halide developer, a silver halidesolvent and an organic film-forming colloid, said base layer havingdispersed therein a lead salt soluble at least in part in said liquid.

9. The product of claim 8 wherein the lead salt is located adjacent onlythat surface of said base layer which adjoins said photosensitive layerwhen said layers are superposed.

10. The product of claim 8 wherein the solution is an aqueous solutionand the organic filmforming colloid dissolved therein is sodiumcarboxymethyl cellulose, and the sheet support is baryta paper.

11. The product of claim 10 wherein the aqueous solution includeshydroquinone, sodium thiosulfate and sodium hydroxide, and the lead saltis lead acetate.

12. A photographic product capable of forming transfer prints inconjunction with a photosensitive silver halide element, said productcomprising a rupturable containing means holding a liquid and a sheetsupport upon which said containing means is mounted, said sheet supportproviding an image-receiving area adjacent said containing means onto.which said liquid is spreadable'in athin layer directly from'saidcontaining means, said product carrying a silver halide developer, asilver halide solvent and a leadsa-lt soluble in part at least in saidliquid, said reagents and said liquid being sufficient in amount andbeing so located in relation to said image-recei'vingarea that thespreading of said liquid over said areadisperses silverhalideJdeewithvsaid colloid to egiveiax reactionproduct less il! 14. Theproduct; oficlaimdzn wherein. :the lead.

e's'oluble in said liquid than; said: colloid.

salt is leadacetatel il5. "The product ofuclaim. l2 wherein:zthe leadsalt is lead tartrate.

taining means comprises a tsingleselongatediem closure V which containszall of said" liquid, and an elong'ated dispensinglipr. which. parallelsi.said aenclosure and eissrupturahlez. tozprovide aipassage fors s'aidliquid.

I F '17; fThezproduct-bf zclaim .12; wherein ,thecontaining meanscomprises;a pairrofziliquideconeta-mine enclosures,.eacl'nincludlngcarupturable 'iliquid-jdispensing lip fxfor .zproividing11a passage 7 ther'efrom to .-vsaid .:image-receiving' 1e'..area,-f.the:illiquid: in ones-(soft:saidziienclosures..z:comprising aifd-ispersion:aofitheesilvernhalide; solvent' 'and', 'the silveriihalidesdeveloper, .:;and ?the :liquid :in -the :\:-'dther:.-:ofs:;said-.:enclosures :.comprising--:a 'dispersaid 'imagewise distribution' ofsaidgsoluble 'silver *complex to an image-carrying: :layer':so:super- Vposed adjacent said emulsion 'layer as to receive a depthwise diffusionor said solution from saidemulsion" layer without appreciably to silverthe silver ions :of said soluble s'ilver complex in the 'presence of' alead salt soluble saidsolution to form an-image' in silver which=is-a'po'sitive of the-subject matter of said -latent "image.

"24; The process of claim 23 wherein the lead salt iscarried in's'olidfornr-by saidimage-carryl The:producttofzclaimi'1'7 whereintherdis- V V persions are solutions; :19. miphotographiczproducthcapableof forming transfer prints in conjunctionawvith-aa. photosensitiveFISllVel :2 halide element, z'sai'd product e'omprisingearupturabletcontaining.:means hold- ':ing an:alkalineiliquidzsolutiomofiaacsilver halide l; developer ,:.a .s'ilverhalide solventigand' arr: organic -Cfilmeforming::uolloidgtaiid;asheetzzsupport :u'pon twh-ichysaid containing": means .:is: .mounted,:said ei'sheet 'isupport providing; an images-receiving: area adj aeentsaid: containing means :conto. :which. said -i11quidsolutions. isspreadable gin; a. .thin; layer ,di-

ire'ctlyxirom said: 'containing..:means; :said; support iihavingdistributed, 2 at least throughout said.

image-receiving. area,:. a'lead; :s'altsoluble .:in;saidz;solution;zsairtisolutiongandcsaidrplead salt being z zsufiicient; in:ramonnt Lsoxth'at: therzspreadingeof :said;;liquid .-'Over:-sa;idaiarea1 provides. a; dispersion of. .rsilverahalidegdeueloper,::.si1ver ::ha1ide;:- solvent film-forming colloid dissolved-thereinissodium ezcar'boxymethyl --.cellulose, and: the sheet support :is 1barytapaper.

22. The product of :claim ;'21"Wher8in' the aqueous solution 1 includesehydroquinone, so

iidium. thiosulfate vsand @sodium hydroxide, and

:Ithei lead:1salti.is lead acetate.

23;.Thezprocessiofstorming. positive images .in rrsilverwhichicomprisesdeveloping alatent neg- :ative :image. insasilverthalide. emulsion layer swith ax solution-comprising-a. silverhalide .de- .1 velopert and l. a: silver: halide solvent: to form an i.imagewise distribution ;of;soluble silver complex ;:in:saidsiemulsionzzlayer, :transferring from said --emulsion1ayerby'z'imbibition at.. ;least. part .Of

inglayer in a position to bedissolvedfin' the solution.

"25."The processpfclainr-Zt-wherein the lead 7 .salt is dispersedadja'centonly' the surface of sensitive layer.

-26.'-The;process of claim=23"wherein a liquid containing an"01'ganicfilm' forming colloid ;-'-is "spread in a 'layer generaily; parallel toand: ad-

"ja'cent the photosensitive emuision in a' position to permeate saidemulsion *and gproVides 'sthe liquid-for the solution'ofthe-silverhalide developer and the silver halide solvent.

7 '27. The process cram-1m 26 wherein'the-liquid is spread-between the,silver halide emulsion layerand the image-carrying' layer, and the "leadsaltreacts with the film -forming eolloidin the liquid layer" to formtherewith a reaction product more insoluble in the liquid than thecolloid.

28. The-process of claim 27' wherein the lead salt is lead acetate.

29; A photographic product 1 capable or form- *ing-tran'sfer prints-inconjunction "with a photo- "sensitive silver" halide element, said"product comprising a rupturable containing means" hold- "ing'a liquid"and" a sheet" support upon-"which said "containing" means is 'mounted,said sheet support" providing 'an.-'-image-receiving area adjacentsaidcontaining means 'onto which said liquid is sprea dable in a thinlayer directly from "said containing means; said product carrying a lead'salt -soluble in partat "least in'said liquid and also at leastonesubstance from the class consisting of the silver halide 1 developersand the silver halide solvents; :said liquid beings-suificient' intamount and beingi-so located inzrelation -to said image receiving areathat 1 the spreading'ofsaidliquidt'over said area disperses:zsaidssubstance and; .leadi'sa'lt throughout ;:said .area'? in adequatequantity..:to:participate in the formation of a transfers-print ofaslatent'. image in an area of a contiguous silver'halide. element 2equivalenttrto said :imageereceiving v area.

."E'D'WIN LAND.

JREFERENCES CITED "iThe following" references are of record 'in" theitle of this patent:

'JUNITED. STATES PATENTS E-Number if Name Date 2312 954 :iBlain::*Feb..:24,I 1885 1,610,888 itifelley ..'I Dec. '14,; 1926l',9:lifi';350 :Wendt. July .4,1.:l.933 1 ,963,707 LeJeune :June 19,1934.5 2,691 639 .rRllSSEll ;:'Aug. 31, 1937 "32,217,169 *Sus Oct." 8,i 1940123224269 Ivlelntosh 1 Dec. 10,; 19,40

:{vQihCP TBf-CKBHUQS on fcllowingpage) said image-carryinglayer-adjacent the photo- 14 Country Date Great Britain May 8, 1930Great Britain May 12, 1932 Great Britain May 3, 1933 Great Britain July26, 1934 France Mar. 10, 1943 OTHER REFERENCES Beveridge: Paper MakersPocket Book," D.

10 Van Nostrand & Company, 1925, page 238 cited.

Wall: Intensification and Reduction, American Photographic Publishing00., 1927, page 15 Photography Theory and Practice. Pitman Publishing(10., pages 355-? cited 2d edi- UNITED STATES PATENTS Number Number NameDate 3581762 2,224,654 McIntosh Dec. 10, 1940 3 2,637 2,322,005 FierkeJune 15, 1943 a 391,790 2,322,006 Fierke June 15, 1943 413,853 2,322,027Jelley June 15, 1943 879,995 2,352,014 Rott June 20, 1944 2,355,884McIntosh Aug. 15, 1944 FOREIGN PATENTS Number Country Date 12,678 GreatBritain July 22, 1899 of 1 99 cited 1311).).

10,051 Great Britain Apr. 30, 1906 Clerc- 24,667 Great Britain 1906 15 u1937 13,835 Great Britain 190*! 1

1. A PHOTOGRAPHIC PRODUCT COMPRISING A PHOTOGRAPHIC PRODUCT COMPRISING APHOTOSENSITIVE MATERIAL WHICH INCLUDES A SILVER HALIDE LAYER, A BASELAYER FOR RECEIVING, BY TRANSFER, A POSITIVE PRINT, AND A RUPTURABLECONTAINING MEANS HOLDING A LIQUID, SAID PRODUCT HAVING POSITIONEDTHEREIN PHOTOGRAPHIC REAGENTS INCLUDING A SILVER HALIDE DEVELOPER, ASILVER HALIDE SOLVENT AND A LEAD SALT SOLUBLE IN SAID LIQUID, SAIDCONTAINING MEANS AND SAID LAYERS BEING SO HELD TOGETHER THAT SAIDCONTAINING MEANS IS CAPABLE, UPON RUPTURE, OF RELEASING AT LEAST PART OFITS CONTENTS TO PERMEATE SUPERPOSED PORTIONS OF SAID PHOTOSENSITIVELAYER AND SAID BASE LAYER, SAID LIQUID, UPON RELEASE, RENDERING SAIDSILVER HALIDE DEVELOPER AND SAID SILVER HALIDE SOLVENT EFFECTIVE TODEVELOP A LATENT IMAGE IN SAID PHOTOSENSITIVE LAYER AND TO FORM SOLUBLESILVER COMPLEX WITH THE UNDEVELOPED SILVER HALIDE OF SAID PHOTOSENSITIVELAYER AND, ADDITIONALLY, PROVIDING A SOLUTION OF THE LEAD SALT ADJACENTTHE SURFACE OF THE PRINT-RECEIVING AREA OF SAID BASE LAYER IN WHICH PARTAT LEAST OF THE SOLUBLE SILVER COMPLEX IS REDUCED TO SILVER TO PRODUCETHE POSITIVE PRINT.
 23. THE PROCESS OF FORMING POSITIVE IMAGES IN SILVERWHICH COMPRISES DEVELOPING A LATENT NEGATIVE IMAGE IN A SILVER HALIDEEMULSION LAYER WITH A SOLUTION COMPRISING A SILVER HALIDE DEVELOPER ANDA SILVER HALIDE SOLVENT TO FORM AN IMAGEWISE DISTRIBUTION OF SOL,UBLESILVER COMPLEX IN SAID EMULSION LAYER, TRANSFERRING FROM SAID EMULSIONLAYER BY IMBIBITION AT LEAST PART OF SAID IMAGEWISE DISTRIBUTION OF SAIDSOLUBLE SILVER COMPLEX TO AN IMAGE-CARRYING LAYER SO SUPERPOSED ADJACENTSAID EMULSION LAYER AS TO RECEIVE A DEPTHWISE DIFFUSION OF SAID SOLUTIONFROM SAID EMULSION LAYER WITHOUT APPRECIABLY DISTURBING THE IMAGEWISEDISTRIBUTION OF THE SILVER COMPLEX IN SAID SOLUTION, AND REDUCING TOSILVER THE SILVER IONS OF SAID SOLUBLE SILVER COMPLEX IN THE PRESENCE OFA LEAD SALT SOLUBLE IN SAID SOLUTION TO FORM AN IMAGE IN SILVER WHICH ISA POSITIVE OF THE SUBJECT MATTER OF SAID LATENT IMAGE.